prm2d: Memory manager out of usable memory

[gb karki]

Hi Expert,

I have checked memory utilization is vary between 91-93 % but I'm continuously getting below messages.

Feb 24 09:31:49 frcgrwta HP-PRM: [2165]: prm2d: Memory manager out of usable memory. no changes made
Feb 24 09:31:58 frcgrwta above message repeats 11 times
Feb 24 09:31:49 frcgrwta HP-PRM: [2165]: prm2d: memory group 10 requested 70 pages, set to minimum 256.
Feb 24 09:37:32 frcgrwta HP-PRM: [2165]: prm2d: Finished moving PID 2400 to MRG 1

can you please give me any idea?

Regards
G

[Don Morris_1]

Well, this is a bit of a guess since either you didn't include the message saying what changes were being attempted or it wasn't logged -- but my assumption would be that prm was attempting to either create a new memory group or expand the size of an existing one and received ENOMEM. That would mean one of the following:

1) The memory group in question pre-reserves memory and insufficient free memory (physical, memory swap, lockable) was available. Shouldn't be the case here as I don't believe PRM is allowed to create pre-reservation memory groups.

2) The memory group in question was unable to acquire lockable memory from the User memory class. The default memory group will retain 10% of the User memory class lockable memory as its total lockable memory -- so this may be the case here [if what's going on is that the non-default groups are pushing 90% of user memory leaving only 10% in the default memory group, I would expect you'd see this]. Another possibility is that default group is simply out of lockable memory because it is already consumed by mlock/plock using clients.

3) The memory group in question was unable to acquire sufficient physical memory or memory swap from the default memory group. Pretty much the same story as the above (the 10% of the User Memory Class applies to physical/memory swap as well for the Default memory group), except mlock/plock clients don't factor into this. Note that in the physical case, the memory does not have to be necessarily free -- the 10% is based on the physical memory assigned to the group [the accounting balances out later].

You don't say how you're measuring memory utilization (is that system-wide or just utilization within the User memory areas? The System-wide utilization is somewhat irrelevant here since PRM is only redistributing memory between groups in the User Memory Class). You also don't mention what OS this is, which has an impact as well -- on v3, UFC uses a memory group within the User Class as well, and hence it will affect the resources PRM has available (the minimum size of UFC is what's important -- maximum above minimum is interesting from a consumption point of view, but doesn't play into this accounting).